Note: Descriptions are shown in the official language in which they were submitted.
W093t21013 ~A ~ 4 -1- PCl/US92/0380~ ~
TITLE OF THE INVENTION
SOFT STRETCHABLE COMPOSITE FABRIC
FIELD OF THE INVENT10~1
This invention is related to stretchable layered composite
fabrics, more particularly, to layered composite fabrics which
provide barrier properties with water vapor permeability.
;~ BACKGROUND OF THE INVENTION
..
Knitted fabrics are generally softer, more drapeable, offer
less resistance to stretching and can be stretched without damage
further than woven fabrics. These comfort related properties are
very important considerations in the design and manufacture of many
types of lightweight or close-fitting garments.
~ ,
Lightweight knitted fabrics have a relatively open `-
construction, exhibit high air permeability and, consequently, haYe
virtually no barrier properties such as windproofness or thermal
insulation qualities. This severely limits the outdoor
applications in colder weather without additional outer layers.
It is very desirable to enhance the barrier properties of the
lightweight knitted fabrics while continuing to provide comfort
related properties such as softness, drapeability, stretchability,
stretch-recovery and water-vapor-permeability.
SUMMARY OF THE IN~/ENTION
This invention provides soft drapeable stretchable water-
vapor-permeable layered composite materials having low tensile
modulus in the transverse direction and having functional
properties such as windproofnesst water-vapor-permeabilityt weather
resistance or waterproofness.
8y tensile modulus" it is meant the resistance of a material
to be stretched or elongated. It is expressed herein in terms of
w 0 93/21013 C ~ 2 i I /6~ ` -2- PCT/US92/0380X
the force (F) required to stretch or elongate the material a
specified distance (D).
By "windproofness" it is meant a low rate of permeability of
air through the material. It is expressed herein in term~ of the
s volume of air (cm3) passing through a given area (cm2) in a given
time (min) under a given pressure drop (mm water pressure).
The force to displacement (F/D) ratio as used herein is the
ratio obtained by dividing the tensile force ~expressed in Newtons)
to stretch a 2.54 cm wide specimen to 1.25 times its original
o length (25% extension) by the displacement (expressed in
centimeters) to reach 25% extension.
Transverse direction is used herein to indicate the direction
in the plane of manufacture perpendicular to the machine direction
(direction of manufacture). The materials of the layers described
herein are considered to be planar, defined by their length
(machine direction) and width (transverse direction).
The composite material of the invention can comprise a layer
of porous film adhesively laminated to a 7ayer of fabric; the
- porous film and the fabric each having, at 25% extension in the
transverse direction, an F/D ratio per 2.54 cm width less than 3.5;
and the composite material having an F/D ratio less than 9Ø
Another embodiment of the composite material of the invention
can comprise a layer of porous film to each side of which is
adhesively laminated a layer of fabric; the porous film and the
fabric each having, at 25X extension in the transverse direction,
an f/D ratio less than 3.5; and the composite material havin~, at
25% extension in the transverse direction, an F/D ratio less than
9Ø
By "porous" is meant that the film has pores or voids from one
side to the other.
To enhance barrier properties such as windproofness or
waterproofness the porous film of the embodiments above may be
- coated with a continuous substantially air-impermeable layer of
hydr~Rhilic water vapor-permeable polymer, e.g. a polyurethane,
which prevents passage of liquid water through it, but has high
water-vapor-permeability.
The stretchtble water-vapor-permeable layered composite
material of the invention has excellent drape characteristics and
W093/21013 ~A ~ i 1 I h~4 3 PCr/US92/03XOX
can be substantially stretched in the transverse direction by
application of very low forces without loss of important functional
characteristics such as windproofness, water-vapor-permeability,
weather resistance or waterproofness.
s To enhance these properties, the axes of lower tensile modulus
of the layers of the composite are aligned in substantially
parallel orientation.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The layered composite materials of the invention are
lo engineered to enhance softness, drape, stretchability and stretch-
recovery, and to minimize resistance to stretching in the
transverse direction, first through selection of component
materials, each preferably having high softness, drape,
stretchability and stretch-recovery, and each having lower tensile
modulus in the transverse direction than in the machine direction;
and secondly, in contrast to conventional practices, by aligning
the axis of lowest tensile modulus of each layer in the same
direction with respect to its neighboring layers. Thus, it can be
seen that an important element in the construction of the layered
composite material of the invention is the relative orientation of
the tensile properties of each layer.
A preferred embodiment of the stretchable water-vapor-
- permeable composite material of the invention comprises a layer of
porous film adhesively laminated to a layer of fabric. Another
preferred embodiment of the invention comprises a layer of porous
film to each side of which is adhesively laminated a layer of
fabric.
~he porous film may have a pore volume in the range 40 - 95
percent, preferably 60 - 95 percent; a mean pore s~ze smaller than
~- 30 about 2 m~crometers, preferàbly smaller than 1 ~icrometer; air
;~ permeability less than about 91 cubic centimeters/minute/square
~; centimeter at a pressure drop of 12.7 millimeters water; lower
tensile modulus in the transverse direction than in the machine
direction, and an F/D ratio, at 25% extension in the transverse
3s direction, less than 3.5. The porous film may be a membrane, mesh,
WO 93/21013 C A ~ I 1 / 6 ~ 4 PCl/US92/0380X
or nonwoven web selected from, but not limited to the group:
polyolefin, polyamide, polyester, polyurethane, fluoropolymer, and
the like. Such films are known in the art and are commercially
available. The preferred film is porous polytetrafluoroethylene,
more preferably, porous expanded polytetrafluoroethylene film
having a porous structure of interconnected nodes and fibrils as
described in USP 3,953,566 (Gore) and USP 4,187,390 (Gore), and is
manufactured by W.L.Gore and Associates, Inc.
The porous film may be coated with a continuous substantially
air-impermeable layer of hydrophilic water-vapor-permeable polymer.
The coating increases the barrier properties of the porous film
such as liquid water penetration resistance, windproofness, and
; heat transfer resistance while continuing the important comfort
related properties of water vapor transmission through the film and
low tensile modulus; the coated film having, at 25% extension in
the transverse direction, an F/D ratio less than 3.5.
Hydrophilic water-vapor-permeable polymers are known in the
art and are avaitable commercially. Most preferred for the coated
film of the composite material of the invention-is a hydrophilic
water-vapor-permeable polyurethane polymer of the type described in
USP 4,194,041 (Gore,et al) or, alternatively, of the type described
in USP 4,532,316 (Henn).
The fabric of the layered composite material of the invention
; has lower tensile modulus in the transverse direction than in the
machine direction and an F/D ratio, at 25% extension in the
transverse direction, less than 3.5. Knit fabric is preferred for
- its ability to stretch and recover from stretching. Most preferred
is circular knit fabric. Circular knit fabric includes both single
knit and double knit fabric of the type: Jersey, double jersey,
jacquard double jersey, interlocks, narrow and broad rib, and the
like. Furthenmore, the fabric may be processed to provide greater
loft as exemplified by fleece, pile, brushed, or velour fabrics,
and the like. Such fabrics are well known to have high softness,
drapeability, stretchability and stretch-recovery.
3s The fabric can be made from yarn of synthetic fibers or
natural fibers, or blends of synthetic and natural fibers,
depending on the intended application of the fabric. For example,
for external wear and outer garment use fabric of polyamide,
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polyester, polyacrylic, or other synthetic fibers may be preferred
for their mechanical properties and environmental resistance. On
the other hand, for inner wear or undergarment applications, where
fabric hand, skin-~eel, water wicking and heat transfer properties
assume much greater importance, natural fibers such as cotton or
wool may be preferred.
The adhesive to bond together the layers of the composite
material of the invention may be selected from many known in the
art. Suitable adhesives may be found in, but not limited to, the
class consisting of thermoplastic polymers, thermosetting polymers,
or reaction curing polymers. They may be applied to the surfaces
to be laminated by conventional means, for example by coating or
printing methods. Also, in embodiments incorporating the coated
film described hereinabove, the hydrophilic polyurethane polymer of
the coating may be used to adhesively bond the coated film layer to
the fabric layer. The method and material selected for adhesively
bonding the layers is based on end use requirements projected for
the composite material.
TEST DESCRIPTlONS
WATER VAPOR TRANSMISSION RATE (WTVR)
. -
A description of the test employed to measure water vapor
transmission rate (WVTR) is given below. The procedure has been
found to be suitable for testing films, coatings, and coated
products.
2S In the procedure, approximately 70 ml. of a solution
consisting of 35 parts by weight of potassium acetate and 15 parts
by weight of distilled water was placed into a 133 ml.
polypropylene cup, having an inside diameter of 6.5 cm. at its
mouth. An expanded polytetrafluoroethylene (PTFE) membrane having
a minimum WVTR of approximately 85,000 9/m2/24 hrs. as tested by
the method described in U.S. Patent 4,862,730 to Crosby and
available from W. L. Gore & Associates, lnc. of Newark, Delaware,
was heat sealed to the lip of the c~p to create a ~aut, leakproof,
microporous barrier containing the solution.
W O 93/21013 ~ A ~ 4 -6- PCT/US92/03~0X
A similar expanded PTFE membrane was mounted to the surface of
a water bath. The water bath assembly was controlled at 23C plus
0.2C, utilizing a temperature controlled room and a water
circulating bath.
s ~he sample to be ~ested was allowed to condition at a
temperature of 23C and a relative humidity of 50X prior to
performing the test procedure. Samples were placed so the
microporous polymeric membrane was in contact with the expanded
polytetrafluoroethylene membrane mounted to the surface of the
water bath and allowed to equilibrate for at least 15 minutes prior
to the introduction of the cup assembly.
The cup assembly was weighed to the nearest 1/10009. and was
placed in an inverted manner onto the center of the test sample.
Water transport was provided by the driving force between the
lS water in the water bath and the saturated salt solution providing
water flux by diffusion in that direction. The sample was tested
for 15 minutes and the cup assembly was then removed, weighed again
within 1/10009.
The WVTR of the sample was calculated from the weight gain of
the cup assembly and was expressed in grams of water per square
meter of sample surface area per 24 hours.
TENSILE TEST
The tensile properties of the materials were determined using
a constant rate-of-jaw separation type machine (Instron testing
machine, Model 1122).
Materials were cut into 2.54 centimeter wide strips in both
machinè and transverse directions. Samples were allowed to
condition in a controlled room at a temperature of 21-C and 65%
relative humidity.
The gauge length of the test was 5.08 centimeters and the
strain rate was 500% / minute. All samples were tested to break.
The tensile modulus of the materials is reported as the force
to displacement (F/D) ratio obtained by dividing the tensile force
(expressed in Ne~tons) to stretch a test specimen to 1.25 times its
W0 93/21013 ~ 4 -7- PCI/US92/0380X
original length (25% extension) divided by the displacement
(expressed in centimeters) to reach 25% extension.
AIR PERMEABILITY - Hiqh Flow Rate Method
Air permeability was measur2d by clamping a test sampie in a
~- 5 gasketed flanged fixture which provided a circular area of
approximately 39 square centimeters (about 7 centimeters diameter)
for air flow measurement. The upstream side of the sample fixture
was connected to a flow meter in line with a source of dry
compressed air. The downstream side of the sample fixture was open
to the atmosphere.
Testing was accomplished by applying a pressure of 12.7
millimeters of water to the upstream side of the sample and
recording the flow rate of the air passing through the in-line
flowmeter (a ball-float rotameter).
lS The sample was conditioned at 70-F and 65% relative humidity
for at least 4 hours prior to testing.
Results are reported as cubic centimeters/minute/square
centimeter of sample, at 12.7 millimeters water pressure.
AIR PERMEABILITY - Low Flow Rate Method
The resistance of samples having relatively low air
permeability flow was measured by a Gurley densometer (ASTM D726-
58j manufactured by ~. ~ L.E. Gurley ~ Sons. The results are
obtained in terms of Gurley Number which is the time in seconds for
100 cubic centimeters of air to pass through 6.45 square
centimeters of a test sample at a pressure drop of 12.4 centimeters
of water.
PORE SIZE MEASUREMENT
Pore size measurements are made by the Coulter Porometer (TM),
;~- manufactured by Coulter Electronics, Inc., Hialeah, FL.
0 The Coulter Porometer (TM) is an instrument that provides
,
WO93/21013 !~ A ~ 8- PCT/US92/0380X
automated measurement of pore size distributions in porous media
using the liquid displacement method (described in ASTM Std. F316-
86).
EXAMPLES
ExamDle 1
This example demonstrates a three-layer embodiment of the
stretchable water-vapor-permeable composite material and employs
- the following materials: two layers of a circular knitted fabric
piled on one side, and a porous polymeric film.
The knitted napped fabric was made from a polyester yarn, had
lower tensile modulus in the transverse direction than the machine
direction and weighed 122 g/m2. The knitted napped fabrics, Styles
#7868 and #7869, were obtained from Malden Mills, Lawrence, MA
01841. Properties are shown in Table 1.
The porous polymeric film was a porous expanded
polytetrafluoroethylene film as described in USP 3,953,566 (Gore),
- manufactured by W.L.Gore ~ Associates, Inc. of Newark, DE. Thefilm was prepared from polytetrafluoroethylene fine powder using
paste extrusion and calendering techniques and was expanded in both
machine direction and transverse direction. The porous expanded
pol~ytetrafluoroethylene film had lower tensile modulus in the
transverse direction than the machine direction, weight of about 4
grams/m2, pore volume of about 82%, and thickness of about 12
micrometers. Addittonal properties are shown in ~able 1.
2S The 3-layer composite material was prepared by a lamination -`
process. The sequence of the lamination process was (1) `
application of adhesive by a gravure roll to one side of the porous
expanded polytetrafluoroethylene film, (2) combining a layer of the
knitted napped fabric to the adhesive side of the film by nipping
between two rolls, (3) application of adhesive by a gravure roll to
-the fi1m side of the resulting 2-layer compos~te, and (4) combining
a second layer of knitted napped fabric to the film side of the
composite by nipping between two rolls.
, The lamination equipment was a multi-roll stack configuration
w o 93/21013 ~ A~ 4 PCT/US92/03808
laminator which had a heated metal gravure printing roll. A feed -
reservoir on the heated gravure printing roll contained hot melt -
polyurethane adhesive of the type described in USP 4,S32,316 (Henn)
which was printed in a discontinuous pattern on the porous expanded
polytetrafluoroethylene film as it passed through the nip of the ~;~gravure roll and a metal press roll. The adhesive printed film was
then adhered to the non-napped surface of the circular knitted -fabric by passage through the nip of the metal press roll and a
silicone rubber surfaced roll, thus forming a 2-layer composite
material.
~he 2-layer composite material was then fed to a second multi-
roll stack configuration laminator. As described above, the
adhesive was printed in a discontinuous pattern on the porous
expanded polytetrafluoroethylene film of the 2-layer composite ;material which was then adhered to t~e non-napped surface of the
second layer of circular knitted fabric to form a 3-layer
stretchable water-vapor-permeable composite material in which the ~-
axes of lower tensile modulus of the materials of the layers are in
parallel alignment. ~-The pattern of adhesive application and the amount of adhesive
applied can also influence the softness, drape and feel of the
composite material as well as the mechanical properties of the
composite material such as bond strength, stretch and stretch-
. .
recovery. It is recognized 1n the art that, for lamination of
different knltted fabrics than used in the example above, some ~`
.
experimentation may be needed to detenmine the optimum adhesive ~`
laydown pattern and amount to obtain the deslred properties in the
composlte material.
Table 1
Fabric 1 Fabrlc 2 Both eP~FE 3-Layer i``
ProDertY #7868 #7869 Fabrlcs Film Laminate '`
WVTR ~ ~ 12950 13670 7815 >80000 7675
Air Permeabllity>3000 >3000 NM 39.6 ~!30.5
F/D Ratio (trans.) 2.63 1.37 NM 1.08 6.84
(cm3/min/cm2 at 12.7 mm water pressure)
NM ^ (Not Measured)
. -
.
.... ... .. .. .... . .
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The 3-layer stretchable water-vapor-permeable camposite
material of Example I had excellent softness and drape
characteristics. It required a low force to stretch at least 25%
s and exhibited stretch-recovery greater than 90%. It also had
excellent windproofness, as indicated by the low air permeability
values in Table I, and excellent WVTR properties.
' ~ '
ComDarative ExamDle 1
A three-layer composite material was prepared for comparative
purposes. Materials and processing were as described in Example I
above except that a tifferent porous polymeric film was used.
~ he porous polymeric film was a porous expanded
polytetrafluoroethylene film as described in USP 3,953,566 (Gore),
manufactured by W.L.Gore ~ Associates, Inc. The membrane was
prepared from polytetrafluoroethylene fine powder using paste
extrusion and calendering techniques and was expanded in the
transverse direction. The porous expanded polytetrafluoroethylene
film had higher tensile modulus in the transverse direction, and an
F/D ratio, at 25X extension in the transverse direction, greater
.~ than 3.S. The porous expanded polytetrafluoroethylene film had a
weight of about 17 grams/m2, a pore volume of about 82X, and a
thickness of about 43 micrometers. Properties are shown tn Table
2.
In contrast to the composite materials of the invention, the
layers of the comparative example were oriented such that the axis
of lowest~tensile modulus of the porous expanded
polytetrafluoroethylene film was perpendicular to the axis of
lowest tensile modulus of the fabric.
.-~ :: ,
'~
'
. :
W O 93~21013 ~ A ;~ pc~r/us92/o38o8
Table 2 ~-
Fabric 1 Fabric 2 Both eP~FE 3-Layer
ProDertY ~7868 #7869 Fabrics Film Laminate ;
s WVTR 12950 13670 7815 >80000 7675
Air Permeability *>3000 >3000 NM <30.5 <30.5F/D Ratio (trans.) 3.64 1.37 NM 11.6 16.2
* (cm3/min/cm2 at 12.7 mm water pressure) `-
NM - Not Measured
The material of the comparative example had relatively poor
softness and drape characteristics compared to the material of
Example 1, and the force required to stretch the material 25% was
excessive.
.
ExamDle 2 '`~
This example demonstrates a two-layer embodiment of the
stretchable water-vapor-permeable composite material and employs `r''~'
the following materials: a layer of circular knitted brushed cotton
fabric, and a porous polymeric film coated with a continuous
substantially air-impermeable layer of hydrophilic polyurethane ~`
polymer. !~
The circular knitted brushed cotton fabric was Style 6900
fabric obtained from Milliken ~ Co. The fabric had lower tensile `
modulus in the transverse direction than in the machine direction
and a weight of approximately 170 g/m2. Additional properties are
shown in ~able 3.
~he porous polymeric film was a porous expanded
polytetrafluoroethylene film as described in USP 3,953,566 (Gore),
manufactured by ~.L.Gore ~ Associates, Inc.. The film was prepared
from polytetrafluoroethylene fine powder using paste extrusion and
calendering technlques and was expanded in both machine direction
and transverse direction. The porous expanded
polytetrafluoroethylene film had lower tensile modulus in the
transverse direction than in the machine dlrection, a weight of
about 2-3 grams/m2, a pore volume of about 82X, and a thickness of
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about 8 micrometers Additional properties are shown in Table 3
The 2-layer composite material was prepared by a lamination ;
process in which the porous expanded polytetrafluoroethy~ene film
was (1) coated w1th a continuous layer of hydrophilic polyurethane
s polymer and then (2) combined with the kn1tted brushed cotton
fabric by nipping between two rolls; the continuous layer of
hjdrophilic pol~urethane served as ~dhesive to bond the layers
together The hydrophilic polyurethane polymer was a reactive hot
melt hydrophilic polyurethane prepared according to the teachings
of USP 4 532 316 (Henn)
The coating/lamination equipment used was a roll coater in a -~
4-roll stack configuration The stack included a heated metal
gravure roll having ~ mounted feed reservoir containing the hot
melt polyurethane po~ymer The gr~vure roll transferred the
lS polyurethane polymer to a fluoroelastomer surfaced roll The
fluoroelastomer surfaced roll appl1ed a continuous layer of the
polyurethane polymer to the surface of the porous expanded
polytetrafluoroethyl-ne f11m as the f11m ~as nipped bet~een the
fluoroelasto~er surfaced roll ~nd a heated ~etal press roll The
fabric was co~b~ned ~1th the porous expanded
polytetrafluoroethylene f~lm on the oppos1te s1de of the metal
press roll as the~ passed through the n1p bet~een the ~et~l press
roll and a s~l~cone rubber surf-ced roll
....
` T~ble 3
: ....
, .
F-br1c ePTFE Co-ted 2-L~jer
ProDèrtv #6900 F11m _Ell~Lamtnate
~VTR N~ ~80000 N~ 18909
A1r Pcr~eab~llty~ >3000 ~6 <0 3 <0 3
F/D Rat~o (trans ) 1 56 0 20 0 68 3 03
* (c~3/~in/cr2 ~t 12 ~ _ n ter prcssure)
NM - Not Measured
T~e 2~ r stretchable ~-ter- n por-perueable co~poslte
~ater1al of Ex-~ple 2 h * exeellent softness and drape
char~cter1st1cs It requ1red very lo~ force to stretch at least
25X and exh1b~ted stretch-recovery gre~ter than 90X It also had
WO93/21013 ~,A~I i io~ -13- PCr/US92/0380X
,
excellent windproofness and excellent WVTR properties.
The low flow rate test method was used to measure air
permeability of the material of Example 2 and, for consistency in
reporting, results were converted to cm3/min/cm2 at 12.7 mm water
s pressure as shown in Table 3.
Due to high uptake of moisture by the composite material of
Example 2, the test time for WVTR measurements shown in Table 3 was ;
extended from 15 minutes to 30 minutes to permit steady state
conditions to be reached.
lo The composite material of Example 2 was fashioned into
undergarments. The undergarments were worn with the brushed cotton
surface next the skin and the coated polytetrafluoroethylene film
surface outward and were found to be unexpectedly comfortable by
the wearers. The mechanically related comfort properties such as
skin-feel, softness, ease of stretching and amount of stretch-
recovery were found to be excellent, however, the greatest surprise
was due to the exceptional temperature/humidity control provided by
the undergarments. The mechanism for this is not fully understood,
but it is felt that the high loft and high moisture wicking
characteristics of the brushed cotton fabric in conjunction with
the high water vapor transmission rate and lack of air movement
through the composite material combine to quickly develop, and then
maintain, a comfortable microclimate next the skin.
